The 386 still has hardware and software interrupts which might just happen between the load and store instructions, so it's not as simple as "we don't need atomics".
If you were writing code specifically for the 386, I suppose you could implement all semaphores as critical sections to guard against external interrupts; I see no reason why that wouldn't work. But realistically, that code would be more of a museum piece than something you'd want to maintain in a 2022 operating system.
If you were writing code specifically for the 386, I suppose you could implement all semaphores as critical sections to guard against external interrupts; I see no reason why that wouldn't work. But realistically, that code would be more of a museum piece than something you'd want to maintain in a 2022 operating system.